Citizen astronomers discover alien planet around four suns

Keck Observatory

Welcome to the second week in October. For most sports fans, this means baseballplayoffs, though for those of us who'd rather stay up all night watching the world Ceres than the World Series, it's time for the annual Division for Planetary Sciences conference. Around 1000 planetary scientists and astronomers converge on a hotel
for a week of talks and poster sessions, each describing some aspect of another world in our solar system—or beyond.

We found out on Monday from the conference that astronomers discovered a new exoplanet. In the company of thousands of candidates, why did the discovery of
this other world make news on our planet? First off, this exoplanet is in orbit around a binary star system, but this particular exoplanet's
binary stars are in orbit around another set of binary stars. Yes, a double-binary system. How recursive!

You usually think of science as happening by stodgy folks in lab coats, off in a windowless room somewhere. The process here is collaborative: Data from
the Kepler spacecraft is posted to a website called Planet Hunters (part of Zooniverse) where ordinary people, who may not necessarily have scientific degrees or formal experience in
astronomy, look for the signatures of planets as they pass in front of other stars. (It turns out that humans are really good at identifying signals from
noise!)

NASA/JPL-Caltech/T. PyleA planet orbiting a binary star.

Once volunteers identify a planetary candidate, astronomers apply for time on big Earth-based telescopes to do follow-up studies. In the case of the
four-star planet, volunteers Kian Jek of San Francisco and Robert Gagliano of Cottonwood, AZ identified the planet candidate, known as PH1.

Using the Keck telescope on Mauna Kea in Hawaii, Planet Hunter Meg Schwamb confirmed that
PH1 was not only in a 137-day orbit around two stars, but that the binary system orbits yet another pair of stars. Astoundingly enough, these orbits are
stable enough to be conducive to planet formation. If you want the nitty gritty details of the discovery, you can read the Planet Hunters team's paper on
the planet in the "quadruple star system".

With 809 confirmed exoplanets—planets in orbit around other stars—discovered to date, the menagerie of other solar systems is growing daily. Spacecraft
such as Kepler have discovered 2,300 exoplanet candidates and the list is only growing.